Digital lighting technologies, i.e., illumination based on semiconductor light sources, such as light-emitting diodes (LEDs), offer a viable alternative to traditional fluorescent, HID, and incandescent lamps. Functional advantages and benefits of LEDs include high energy conversion and optical efficiency, durability, lower operating costs, and many others. Recent advances in LED technology have provided efficient and robust full-spectrum lighting sources that enable a variety of lighting effects in many applications. Some of the fixtures embodying these sources feature a lighting module, including one or more LEDs capable of producing different colors, e.g., red, green, and blue, as well as a processor for independently controlling the output of the LEDs in order to generate a variety of colors and color-changing lighting effects, for example, as discussed in detail in U.S. Pat. Nos. 6,016,038 and 6,211,626, incorporated herein by reference.
It has long been known that light exerts powerful effects on the human brain and on well-being. Light is not only required for vision but also conveys a powerful stimulating signal for human alertness and cognition and has been routinely employed to improve performance and counter the negative impact of sleepiness or so-called “winter blues.” The mechanisms underlying these positive effects of light still remain largely unknown. However, researchers have discovered a new type of light sensitive cell (photoreceptor) in the eye called melanopsin. This photoreceptor has been shown to be an essential component for relaying light information to a set of so-called “non-visual” centers in the brain. In the absence of this photoreceptor, animal research has shown that non-visual functions are disrupted, the biological clock becomes deregulated, and “free-runs” independent from the twenty-four hour day-night cycle become more common.